<template>
  <div class="goods-image">
    <!-- 大图 -->
    <div v-if="show" class="large" :style="[{ backgroundImage: `url(${images[currIndex]})` }, bgPosition]"></div>
    <div class="middle" ref="target">
      <img :src="images[currIndex]" alt="">
      <!-- 遮罩层 -->
      <div v-show="show" class="layer" :style="[position]"></div>
    </div>
    <ul class="small">
      <li v-for="(img, i) in images" :key="img" :class="{ active: i === currIndex }">
        <img @mouseenter="currIndex = i" :src="img" alt="">
      </li>
    </ul>
  </div>
</template>
<script>
import { reactive, ref, watch } from 'vue'
import { useMouseInElement } from '@vueuse/core'
export default {
  name: 'GoodsImage',
  props: {
    images: {
      type: Array,
      default: () => []
    }
  },
  setup(props) {
    // 中图的宽、高
    const middleWidth = 400
    const middleHeight = 400
    // 遮挡层的宽、高
    const coverWidth = 200
    const coverHeight = 200

    // 遮挡层的宽高
    // elementX 鼠标基于容器左上角X轴偏移
    // elementY 鼠标基于容器左上角Y轴偏移
    // isOutside 鼠标是否在模板容器外
    // 定义侦听的dom容器
    const target = ref(null)
    const { elementX, elementY, isOutside } = useMouseInElement(target)
    // 目标：获取遮挡层的left和top值，根据它计算大图的背景图的位置实现方法效果
    // 遮挡层的定位位置
    const position = reactive({ left: 0, top: 0 })
    // 背景大图的起始
    const bgPosition = reactive({ backgroundPositionX: 0, backgroundPositionY: 0 })
    // 侦听遮罩层在中图的移动，来设置遮挡层的定位
    watch([elementX, elementY, isOutside], () => {
      // 设置是否显示预览大图
      show.value = !isOutside.value
      // 控制X轴方向的定位 0-200 之间
      if (elementX.value < coverWidth / 2) {
        position.left = 0
      } else if (elementX.value > (middleWidth - coverWidth / 2)) {
        position.left = 200
      } else {
        position.left = elementX.value - coverWidth / 2
      }
      // 控制Y轴方向的定位 0-200 之间
      if (elementY.value < coverHeight / 2) {
        position.top = 0
      } else if (elementY.value > (middleHeight - coverHeight / 2)) {
        position.top = 200
      } else {
        position.top = elementY.value - coverWidth / 2
      }
      // 设置大背景的定位
      bgPosition.backgroundPositionX = -position.left * 2 + 'px'
      bgPosition.backgroundPositionY = -position.top * 2 + 'px'
      // 设置遮罩容器的定位
      position.left = position.left + 'px'
      position.top = position.top + 'px'
    })
    // 控制是否显示放大镜（鼠标移入到中图时显示放大镜）
    const show = ref(false)

    // 默认显示第1张图片
    const currIndex = ref(0)
    return { currIndex, bgPosition, show, target, position }
  }
}
</script>
<style scoped lang="less">
.goods-image {
  width: 480px;
  height: 400px;
  position: relative;
  display: flex;
  // 显示于内容的上面
  z-index: 500;

  // 大图
  .large {
    position: absolute;
    top: 0;
    left: 412px;
    width: 400px;
    height: 400px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    background-repeat: no-repeat;
    background-size: 800px 800px;
    background-color: #f8f8f8;
  }

  .middle {
    width: 400px;
    height: 400px;
    background: #f5f5f5;
    position: relative;
    cursor: move;

    // 遮挡层
    .layer {
      width: 200px;
      height: 200px;
      background: rgba(0, 0, 0, .2);
      left: 0;
      top: 0;
      position: absolute;
    }

  }

  .small {
    width: 80px;

    li {
      width: 68px;
      height: 68px;
      margin-left: 12px;
      margin-bottom: 15px;
      cursor: pointer;

      &:hover,
      &.active {
        border: 2px solid @xtxColor;
      }
    }
  }
}
</style>